1. Field of the Invention
The present invention relates to a retort sterilization device, a heating device, a heat sterilization method and a heat treatment method, and specifically, to a retort sterilization device including a heating pot for performing sterilization with heating and pressurization.
2. Description of the Related Art
In general, a surface or inside of food has microorganisms such as mold, yeast, bacteria and the like attached or mixed thereto. When the food contains much moisture, such microorganisms make the food rotten. As a food preservation method for avoiding this, drying, salt preservation, low-temperature preservation and the like have been performed from old days. Packaging in film makes it easy to completely block microorganisms. Thus, heat sterilization after packaging is widely used as an effective preservation method.
Heat sterilization is available in dry sterilization, which is performed with heated air, and wet sterilization, which is performed with vapor or hydroheat. Wet sterilization provides a higher sterilization effect because of the amount of heat. A simplest method of sterilization against microorganisms using wet heat is boil sterilization (sterilization in hot water), by which packaged food is put into hot water for sterilization. However, boil sterilization has the following defects. When the heating time is long, the food is deteriorated by heat; and when there is a heat-resistant microorganism which does not die even at 100° C., complete sterilization is impossible under normal pressure.
Thus, when necessary, sterilization with pressurization and heating (retort sterilization) at a temperature exceeding 100° C. is performed. When being warmed in hot water, the food cannot be heated to a temperature higher than the boiling point of water (100° C.). However, when vapor or pressurized hydroheat is used, the food can be heated to a temperature higher than 100° C. Such a method of sterilization is retort sterilization. When the food is heated at a temperature higher than 100° C., the bag packaging the food is burst during cooling because the internal pressure of the bag becomes too high. Therefore, during the cooling, the food needs to be pressurized at a pressure higher than the pressure used for heating and the pressure needs to be adjusted. In order to perform retort sterilization, a device capable of adjusting the temperature, time and pressure precisely is needed. The initial cost is higher beyond comparison than that when a boil sterilization device is used.
For performing retort sterilization on food sealed in a bag of a heat-resistant resin film or the like, the packaging bag is heated with vapor or hydroheat in a retort pot. However, it is difficult to uniformize the heating temperature in the retort pot, and thus the heating temperature may become non-uniform. Japanese Laid-Open Patent Publication No. 2008-301739 discloses a sterilization method, by which sterilization of retort food and cooling after that are performed while the food is slid in a forward-backward direction and in a leftward-rightward direction.
FIG. 16 shows a sterilization device 1000 disclosed in Japanese Laid-Open Patent Publication No. 2008-301739. In the sterilization device 1000 shown in FIG. 16, a rail 220 is provided in a retort pot main body 210, and a movable table 240 is supported by the rail 220 via wheels 230. On the movable table 240, trays 260 having many bags of retort food 250 placed thereon are stacked in multiple stages and supported. The movable table 240 is coupled, via a shaft sealing device 290 provided on the retort pot main body 210, to a driving shaft 285 of a crank mechanism 280 drivable by a motor 270.
When the motor 270 is driven and rotated, the driving shaft 285 of the crank mechanism 280 reciprocates the retort pot main body 210 in association with the rotation of the motor 270, and thus the movable table 240 which supports the trays 260 having the retort food 250 placed thereon is slid. The retort food is sterilized and then cooled while being slid, so that the food is suppressed from, for example, being burned during the sterilization.